Method for synchronously maintaining pdp context status between wireless  communication network and mobile station and associated mobile station

ABSTRACT

A method for synchronously maintaining packet data protocol (PDP) context status between a wireless communication network and a mobile station and an associated mobile station are disclosed to prevent from the asynchronous PDP context status caused by the prior arts. When both the mobile station and the network activate a PDP context for a packet-switched service, if the mobile station is to establish a circuit-switched connection with the network, the mobile station will request the network to suspend the packet-switched service. After the circuit-switched connection is established, the mobile station locally deactivates the PDP context. After the circuit-switched connection is disconnected, if the network informs the mobile station that the packet-switched service is resumed, the mobile station will inform the network that the PDP context is deactivated.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to mobile stations in wirelesscommunication networks, and more particularly to a method forsynchronously maintaining PDP context status between the wirelesscommunication network and the mobile station and an associated mobilestation.

2. Description of the Prior Art

In a GPRS-supported GSM network (called GSM/GPRS network below), when atleast one of the network and the mobile station (also called userequipment) does not support dual transfer mode (DTM), the mobile stationwill not be able to maintain a circuit-switched connection and apacket-switched connection with the network simultaneously. In theGSM/GPRS network, the circuit-switched connection such as a GSM callconnection can provide phone call service, while the packet-switchedconnection such as a GPRS connection can provide data transmissionservice. Thus, when the DTM is not supported, the mobile station cannotestablish the GPRS connection after the GSM call connection with thenetwork is established. This will cause the asynchronous packet dataprotocol (PDP) context status between the network and the mobile stationin some situations.

FIG. 1 shows how the asynchronous PDP context status occurs between themobile station and the GSM/GPRS network in the prior arts. In the flowof FIG. 1, at the beginning, the mobile station (shown as MS) hasalready an activated PDP context used for the packet-switched service(i.e. GPRS service in the GSM/GPRS network). Next, in step 11, if theuser wants to make a GSM call, the mobile station will on one handexecute the GPRS suspension procedure (cf. 3GPP TS 44.018, section3.4.25) to request the network to suspend the packet-switched service,and on the other hand execute the call connection procedure to establishthe GSM call connection with the network. After the GSM call connectionis established, in step 12, if the user no longer wants to use thepacket-switched service and thus needs to deactivate the PDP context,then the mobile station will execute the PDP context deactivationprocedure (cf. 3GPP TS 24.008, section 6.1.3.4) to send out a DeactivatePDP Context Request message, and start the timer T3390 to wait for theresponse of the network. However, since the GSM call connection isestablished, the mobile station cannot establish the GPRS connection soas to transmit the Deactivate PDP Context Request message to thenetwork. Thus, the mobile station will not receive the response from thenetwork until the timer is timeout. Then, according to 3GPP TS 24.008,section 6.1.3.4.3, the mobile station will re-send the Deactivate PDPContext Request message, reset the timer T3390 and wait for the responseof the network again. The above process will be performed repeatedly ifthe mobile station does not receive any response. After the timer T3390has expired for the fifth time, the mobile station will deactivate thePDP context locally so as to release the related wireless resources anddelete the associated information about the PDP context. To “deactivatelocally” means that the mobile station only executes the deactivation ofthe PDP context one-sidedly, without connecting to the network tosynchronously complete the PDP context deactivation procedure therewith.So, the network does not know the mobile station has already deactivatedthe PDP context. Next, in step 13, when the user is to end the GSM call,the mobile station executes the call disconnection procedure; in step14, the network performs GPRS resumption, and indicates whether theresumption is successful in the RR Channel Release message sent to themobile station subsequently. If the GPRS resumption is successful, themobile station determines that there is no need to perform the GPRSresumption and thus the routing area updating procedure will not beexecuted (cf. 3GPP TS 24.008, section 4.7.5.1). This will cause theproblem as below: the PDP context in the side of mobile station isdeactivated while the PDP context in the network side is still inactivated status, such that the PDP context status between the mobilestation and the network is not synchronous. Later, if the mobile stationrequests to establish a GPRS connection, the network will possiblyneglect this request so that the mobile station cannot use the GPRSservice.

SUMMARY OF INVENTION

It is therefore one objective of the present invention to provide amethod for synchronously maintaining PDP context status between thewireless communication network and the mobile station and an associatedmobile station, thereby preventing from the asynchronous PDP contextstatus between the network and the mobile station caused by the priorarts.

In one embodiment of the present invention, a method used in a mobilestation for synchronously maintaining PDP context status between awireless communication network and the mobile station is provided. Boththe mobile station and the wireless communication network activate a PDPcontext for a packet-switched service. The method comprises: requestingthe wireless communication network to suspend the packet-switchedservice when a circuit-switched connection with the wirelesscommunication network is established; deactivating the PDP context afterthe circuit-switched connection is established; and informing thewireless communication network, after the circuit-switched connection isdisconnected, that the PDP context is deactivated when the wirelesscommunication network informs that the first packet-switched service isresumed.

In another embodiment of the present invention, a mobile station forsynchronously maintaining PDP context status with a wirelesscommunication network is provided. Both the mobile station and thewireless communication network activate a PDP context for apacket-switched service. The mobile station comprises: a requestingmeans for requesting the wireless communication network to suspend thepacket-switched service when the mobile station establishes acircuit-switched connection with the wireless communication network; adeactivating means for deactivating the PDP context after thecircuit-switched connection is established; and an informing means forinforming the wireless communication network, after the circuit-switchedconnection is disconnected, that the PDP context is deactivated when thewireless communication network informs the mobile station that the firstpacket-switched service is resumed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows how the asynchronous PDP context status occurs between themobile station and the GSM/GPRS network in the prior arts.

FIG. 2 shows how the problem of the asynchronous PDP context statusbetween the mobile station and the GSM/GPRS network is handled accordingto one embodiment of the present invention.

FIG. 3 is a flow chart of the method for synchronously maintaining thePDP context status between the wireless communication network and themobile station according to one embodiment of the present invention.

FIG. 4 shows part of the data format of the Routing Area Update Requestmessage.

FIG. 5 shows the format of the information element of the PDP contextstatus.

FIG. 6 shows a block diagram of one embodiment of the mobile stationaccording to the present invention.

DETAILED DESCRIPTION

Reference will now to be made in detail to embodiments of the presentinvention, which are illustrated in the accompanying drawings. All theembodiments can be applied to the case where at least one of the mobilestation (for example, but not limited to, the mobile phone) and thewireless communication network (for example, but not limited to, theGSM/GPRS network) does not support the DTM. When the wirelesscommunication network does not support the DTM, it does not necessarilymean that the whole network does not support. Instead, it is possiblethat only part of the network equipments such as cells does not supportwhile the others do. Thus, when the mobile station connects to thenetwork via the network equipment not supporting the DTM, the presentinvention can still apply to.

In the GSM/GPRS network, if the mobile station supports GPRS function,the routing area updating procedure is periodically executed to informthe network of the current routing area where the mobile station islocated. In other specific situations, e.g. when the mobile stationdetermines that the GPRS resumption needs to be performed, it will alsoexecute the routing area updating procedure, as described in 3GPP TS24.008, section 4.7.5.1. However, in step 14 of FIG. 1, if the networksuccessfully performs the GPRS resumption and informs the mobile stationabout that after the GSM call is over, the mobile station will determinethat there is no need to perform the GPRS resumption. Thus, the mobilestation will not also execute the routing area updating procedure sothat the asynchronous PDP context status exists between the mobilestation and the network. Therefore, in one embodiment of the presentinvention, a new specific situation where the mobile station needs toexecute the routing area updating procedure is added, that is, if themobile station has locally deactivated the PDP context previously, thenthe mobile station also needs to execute the routing area updatingprocedure, as shown in steps 21 and 22 of FIG. 2. In step 21, the mobilestation (shown as MS) determines that the PDP context has been locallydeactivated previously, and then in step 22, the mobile station executesthe routing area updating procedure to send out the Routing Area UpdateRequest message to the network. The Routing Area Update Request messageincludes an information element showing the current PDP context status(i.e. deactivated at this situation) in the mobile station. Thus, afterthe network responds the Routing Area Update Accept message to themobile station, the synchronous PDP context status can be reachedbetween the mobile station and the network, as shown in FIG. 2.

FIG. 3 is a flow chart of the method for synchronously maintaining thePDP context status between the wireless communication network and themobile station according to one embodiment of the present invention.This method is used in the mobile station. Before executing the method,both the mobile station and the wireless communication network activatea first PDP context for a first packet-switched service. In step 31,when establishing a circuit-switched connection (e.g. phone callconnection) with the network, the mobile station (shown as MS in FIG. 3)requests the network to suspend the first packet-switched service. Whenthe network is a GSM/GPRS network, the circuit-switched connection canbe a GSM call connection, and the mobile station can execute the GPRSsuspension procedure (cf. 3GPP TS 44.018, section 3.4.25) to request theGSM/GPRS network to suspend the first packet-switched service.

In step 32, after the circuit-switched connection is established, themobile station deactivates the first PDP context locally. The mobilestation can perform this deactivation according to an internalconfiguration or a request of the user. When the network is the GSM/GPRSnetwork, the mobile station will execute the PDP context deactivationprocedure (cf. 3GPP TS 24.008, section 6.1.3.4). If the mobile stationsends out the Deactivate PDP Context Request message five times whilestill receives no response from the network within the timeout of thetimer T3390, then the mobile station deactivates the first PDP contextlocally.

In step 33, after the circuit-switched connection is disconnected, ifthe network informs the mobile station that the first packet-switchedservice is resumed, then the mobile station informs the network aboutthe deactivated status of the first PDP context so as to synchronize thePDP context status between the mobile station and the network. When thenetwork is the GSM/GPRS network, the mobile station can inform thenetwork about the deactivated status of the first PDP context byexecuting the routing area updating procedure to send out the RoutingArea Update Request message, whose data format is partly shown in FIG. 4(also cf. 3GPP TS 24.008, table 9.4.14). The information element of thePDP context status, whose information element identifier (IEI) is 32,can be used to record the current status of the first PDP context. Thus,when receiving the Routing Area Update Request message, the network canupdate the status of the first PDP context according to the informationelement of the PDP context therein, thereby keeping synchronized withthe mobile station.

Preferably, in step 32, the mobile station further stores a deactivationrecord for showing that the mobile station has deactivated the first PDPcontext locally. Then, in step 33, the mobile station informs thenetwork about the deactivated status of the first PDP context accordingto the deactivation record.

The embodiment of FIG. 3 can be extended to the case where two or morePDP contexts have been activated between the mobile station and thenetwork. An embodiment including two activated PDP contexts aredescribed below: in addition to the first PDP context, both the mobilestation and the network have further activated a second PDP context fora second packet-switched service. In this embodiment, each step of FIG.3 is adjusted as follows: in step 31, when the circuit-switchedconnection is established, the mobile station requests the network tosuspend both the first and second packet-switched services; in step 32,after the circuit-switched connection is established, the mobile stationlocally deactivates the first and second PDP contexts; in step 33, afterthe circuit-switched connection is disconnected, if the network informsthe mobile station that the first and second packet-switched servicesare resumed, then the mobile station informs the network that the firstand second PDP contexts are deactivated. When the network is theGSM/GPRS network, the mobile station can inform the network about thedeactivated status of the first and second PDP contexts by executing therouting area updating procedure only once. This is because theinformation element of the PDP context in the Routing Area UpdateRequest message can record the current status of multiple PDP contextssimultaneously, as shown in FIG. 5 (cf. 3GPP TS 24.008, table 10.5.148).Each NSAPI (i.e. network service access point identifier) is one bitvalue for representing the status of one PDP context, wherein 0 and 1represent deactivated and activated respectfully. However, it should benoted that NSAPI(0)˜NSAPI(4) are reserved for other use in the current3GPP specification. Since the informing of the deactivated status ofboth the first and second PDP contexts only needs one-time execution ofthe routing area updating procedure, the signaling load between themobile station and the network can be reduced. Regarding the case wherethree or more PDP contexts have been activated, the method forsynchronously maintaining the PDP context status between the mobilestation and the network can be derived similarly as above.

FIG. 6 shows a block diagram of one embodiment of the mobile station 60according to the present invention. The mobile station 60 is capable ofsynchronously maintaining the PDP context status with the wirelesscommunication network, and comprises a requesting means 61, adeactivating means 62 and an informing means 63. In this embodiment,both the mobile station 60 and the wireless communication networkactivate the first PDP context for the first packet-switched service.The requesting means 61 requests the network to suspend the firstpacket-switched service when the mobile station 60 establishes acircuit-switched connection with the network. The deactivating means 62locally deactivates the first PDP context after the circuit-switchedconnection is established. After the circuit-switched connection isdisconnected, if the network informs the mobile station 60 that thefirst packet-switched service is resumed, then the informing means 63informs the network that the first PDP context is deactivated. When thenetwork is a GSM/GPRS network, the informing means 63 can inform thenetwork about the deactivated status of the first PDP context byexecuting the routing area updating procedure to send out the RoutingArea Update Request message.

Preferably, the deactivating means 62 further stores a deactivationrecord in the mobile station 60 for showing that the mobile station 60has deactivated the first PDP context locally. The informing means 63then informs the network about the deactivated status of the first PDPcontext according to the deactivation record.

If both the mobile station 60 and the network activate the first PDPcontext for the first packet-switched service and a second PDP contextfor a second packet-switched service, then the requesting means 61requests the network to suspend both the first and secondpacket-switched services when the above circuit-switched connection isestablished. Then, after the circuit-switched connection is established,the deactivating means 62 locally deactivates the first and second PDPcontexts. After the circuit-switched connection is disconnected, if thenetwork informs the mobile station 60 that the first and secondpacket-switched services are resumed, then the informing means 63informs the network that the first and second PDP contexts aredeactivated. When the network is the GSM/GPRS network, the informingmeans 63 can inform the network about the deactivated status of thefirst and second PDP contexts by executing the routing area updatingprocedure only once, as explained above.

Please note that all of the requesting means 61, the deactivating means62 and the informing means 63 mentioned above can be realized byhardware, firmware known as a combination of a hardware device andcomputer instructions and data that reside as read-only software on thehardware device, or an electronic system. Examples of hardware caninclude analog, digital and mixed circuits known as microcircuit,microchip, or silicon chip. Examples of the electronic system caninclude system on chip (SOC), system in package (SIP), or computer onmodule (COM).

While the present invention has been shown and described with referenceto the preferred embodiments thereof and the illustrative drawings, itshould not be considered as limited thereby. Various possiblemodifications and alterations can be conceived by persons skilledwithout departing from the scope and the spirit of the presentinvention.

1. A method used in a mobile station for synchronously maintainingpacket data protocol (PDP) context status between a wirelesscommunication network and the mobile station, wherein both the mobilestation and the wireless communication network activate a first PDPcontext for a first packet-switched service, the method comprising:requesting the wireless communication network to suspend the firstpacket-switched service when a circuit-switched connection with thewireless communication network is established; deactivating the firstPDP context after the circuit-switched connection is established; andinforming the wireless communication network, after the circuit-switchedconnection is disconnected, that the first PDP context is deactivatedwhen the wireless communication network informs that the firstpacket-switched service is resumed.
 2. The method of claim 1, whereinthe deactivating step is executed according to request of a user.
 3. Themethod of claim 1, wherein the deactivating step comprises: storing adeactivation record for showing that the mobile station has deactivatedthe first PDP context.
 4. The method of claim 3, wherein the informingstep is executed according to the deactivation record.
 5. The method ofclaim 1, wherein the wireless communication network is a GPRS-enabledGSM network.
 6. The method of claim 5, wherein the informing step isexecuted by executing a routing area updating procedure.
 7. The methodof claim 6, wherein the routing area updating procedure comprisessending a Routing Area Update Request message to the wirelesscommunication network, wherein the Routing Area Update Request messagecomprises an information element indicating a status of the first PDPcontext.
 8. The method of claim 1, wherein both the mobile station andthe wireless communication network further activate a second PDP contextfor a second packet-switched service, the method further comprising:requesting the wireless communication network to suspend the secondpacket-switched service when the circuit-switched connection isestablished; deactivating the second PDP context after thecircuit-switched connection is established; and informing the wirelesscommunication network, after the circuit-switched connection isdisconnected, that the second PDP context is deactivated when thewireless communication network informs that the second packet-switchedservice is resumed.
 9. A mobile station for synchronously maintainingpacket data protocol (PDP) context status with a wireless communicationnetwork, wherein both the mobile station and the wireless communicationnetwork activate a first PDP context for a first packet-switchedservice, the mobile station comprising: a requesting means forrequesting the wireless communication network to suspend the firstpacket-switched service when the mobile station establishes acircuit-switched connection with the wireless communication network; adeactivating means for deactivating the first PDP context after thecircuit-switched connection is established; and an informing means forinforming the wireless communication network, after the circuit-switchedconnection is disconnected, that the first PDP context is deactivatedwhen the wireless communication network informs the mobile station thatthe first packet-switched service is resumed.
 10. The mobile station ofclaim 9, wherein the deactivating means deactivates the first PDPcontext according to request of a user.
 11. The mobile station of claim9, wherein the deactivating means further stores a deactivation recordfor showing that the mobile station has deactivated the first PDPcontext.
 12. The mobile station of claim 11, wherein the informing meansinforms the wireless communication network according to the deactivationrecord.
 13. The mobile station of claim 9, wherein the wirelesscommunication network is a GPRS-enabled GSM network.
 14. The mobilestation of claim 13, wherein the informing means informs the wirelesscommunication network by performing a routing area updating procedure.15. The mobile station of claim 14, wherein the routing area updatingprocedure comprises sending a Routing Area Update Request message to thewireless communication network, wherein the Routing Area Update Requestmessage comprises an information element indicating a status of thefirst PDP context.
 16. The mobile station of claim 9, wherein both themobile station and the wireless communication network further activate asecond PDP context for a second packet-switched service; the requestingmeans further requests the wireless communication network to suspend thesecond packet-switched service when the circuit-switched connection isestablished; the deactivating means further deactivates the second PDPcontext after the circuit-switched connection is established; theinforming means further informs the wireless communication network,after the circuit-switched connection is disconnected, that the secondPDP context is deactivated when the wireless communication networkinforms the mobile station that the second packet-switched service isresumed.